This proposal aims to develop a model of and techniques for assessing visual system toxicity in the human. By combining techniques derived from the Fourier analysis of visual function, combined with visual field mapping, it will be possible to provide a comprehensive description of visual system dysfunction in non-human primates exposed to toxic agents. Coordinated histopathology will enable the investigators to correlate morphologic with functional changes. Prototypical agents to be assayed include: (1) methylmercury, for which sensitive screening tests are required in order to elucidate the time course of progressive visual changes during exposure; (2) carbon monoxide, in order to test the hypothesis that it may induce functional decrements in vision at low luminances; (3) organic solvents, expecially those that seem to be of concern in energy processes, such as toluene, carbon disulfide, and methanol.